What is the appropriate button to use on the product detail page when
the website navigation asks the user to either Shop or Buy?

Of course, can we get a little more interesting and personal? For
example: instead of Shop or Buy can we use buttons that say - 'Go
and Pamper' (for a gifts e-commerce website) or 'Educate Yourself'
(while buying education books) or 'Push Limits' (while e-shopping
for BASE jumping equipment).